This invention pertains to the removal of undesirable material, particularly color bodies, from water-soluble polysaccharide ethers.
Water-soluble polysaccharide ethers are used for their many different properties and are employed in a variety of applications. The polysaccharide ethers are used as thickeners, binders, film formers, water-retention aids, suspension aids, surfactants, lubricants, protective colloids, emulsifiers, and the like, and are used in applications such as foods, cosmetics, pharmaceuticals, latex paints, construction products, ceramics, and a host of other applications. A problem encountered by those that produce and consequently those that use the water-soluble polysaccharide ethers is the presence of contaminants, such as undesirable color and salt. The undesirable color contamination is of particular concern to the pharmaceutical industry.
The color in water-soluble polysaccharide ethers and, in particular, water-soluble cellulose ethers, can vary from a very pale yellow to a golden or even brown hue, depending on the level of color bodies in the product. For some applications the presence of this color is not a problem, but for other applications, in particular tablet coating in the pharmaceutical industry, the colorant causes difficulties. It would be desirable to have a method of removing or reducing the residual color for those applications in which low levels of the color are required.